This invention relates generally to a rigid-disk information-storage system, and more particularly to a miniature, low-mass, gimbaled, head/flexure/conductor assembly for use in and with such a system.
For the purposes of illustration and explanation herein, a preferred embodiment of such an assembly, and of a system employing the same, are disclosed in the setting of an extremely small-format, largely self-contained storage system which employs one or more rotary, rigid, magnetic recording disks. Those skilled in the art, after reading the contents of this specification, will recognize that the invention may be employed in a rigid disk recording system of any size.
The quest for increasing storage density and decreasing costs in rigid medium disk drive data storage systems has focused attention on the need to minimize the separation between the head (transducer) and the media--the so-called "flying height" of the usual air-bearing slider. Improvements in slider and associated manufacture, along with improvements in media surface properties, have enabled the flying height in available rigid disk systems to be reduced to about 0.1-micrometer. Numerous efforts are now devoted to reducing even further the flying height to 0.05 micrometer, or less. These efforts face and present still greater challenges respecting the issue of volume manufacture of sliders, suspensions, media and their assembly and operation in disk drive systems.
With regard to the issue of flying-head technology, significant advances over this prior art technology have been made and are disclosed in the following U.S. patent and co-pending U.S. patent applications: U.S. Pat. No. 5,041,932 for INTEGRATED MAGNETIC READ/WRITE HEAD/FLEXURE/CONDUCTOR STRUCTURE, issued Aug. 20, 1991; U.S. patent application Ser. No. 07/632,958 for METHOD OF MAKING INTEGRATED MAGNETIC READ/WRITE HEAD/FLEXURE/CONDUCTOR STRUCTURE, filed Dec. 21, 1990; U.S. patent application Ser. No. 07/710,561 for INTEGRATED MAGNETIC READ/WRITE HEAD/FLEXURE/CONDUCTOR STRUCTURE, filed Jun. 5, 1991; U.S. patent application Ser. No. 07/710,891 for INTEGRATED MAGNETIC READ/WRITE HEAD/FLEXURE/CONDUCTOR STRUCTURE, filed Jun. 11, 1991; U.S. patent application Ser. No. 07/684,025 for WEAR-RESISTANT HEAD FOR CONTACT READING AND WRITING MAGNETIC MEDIA, filed Apr. 10, 1991; U.S. patent application Ser. No. 07/746,916 for UNITARY MICRO-FLEXURE STRUCTURE AND METHOD OF MAKING SAME, filed Aug. 19, 1991; U.S. patent application Ser. No. 07/760,586 for HIGH-CAPACITY, MICRO-SIZE, RIGID-DISK, MAGNETIC DIGITAL-INFORMATION STORAGE SYSTEM, filed Sep. 16, 1991; and U.S. patent application Ser. No. 07/783,509 for SIZE-INDEPENDENT, RIGID-DISK, MAGNETIC, DIGITAL-INFORMATION STORAGE SYSTEM WITH LOCALIZED READ/WRITE ENHANCEMENTS filed Oct. 28, 1991. The respective disclosures of these documents are hereby incorporated by reference into the present disclosure.
With regard to the above-incorporated materials, in the '932 patent, the patentee describes a very low-mass, integrated head/flexure/conductor structure for continuous sliding-contact operation with rigid media, thereby enabling the minimum possible head/media separation and the maximum achievable recording performance. By reducing "effective mass" (see the '916 patent application) and applied load by two to three orders of magnitude, relative to conventional air-bearing sliders and suspensions, the local pressure exerted on asperities or microscopic contaminants may be kept well below the onset of destructive physical and chemical avalanche processes, which processes lead to catastrophic failure of the head/media interface. Such reduction of the local pressure also helps to reduce the rate of abrasive wear of the head and media and to extend useful operational life.
The validity of the logic behind the development set forth in the '932 patent has been demonstrated in more than two-hundred-thousand hours of wear testing of Flexhead.TM. integrated head/suspension structures on numerous test fixtures (Flexhead.TM. is a trademark owned by Censtor Corp. of San Jose, Calif.). Likewise, read/write tests of these structures, employing, for example, probe-type heads with two-layer perpendicular recording media, have demonstrated a capability for very high recording density. Moreover, the extremely small mass of these structures, and the rigidity of the suspensions, result in high resonant frequencies in the lateral and torsional bending modes, and enable thereby significant improvements in actuator and servo-system design and performance.
With a further specific look at material incorporated by reference above, the pending '025 patent application describes improvements in an integrated head/flexure/conductor structure (such as that set forth in the '932 patent) which improvements provide for the employment of wear-resistant material (a wear-resistant contact pad) in the region which makes contact with the media. This '025 patent application additionally sets forth limitations on the length and width of the wear-resistant contact pad which derive from the need to minimize signal modulation resulting from axial run-out of the disk or other mechanical variance in the drive.
The present invention addresses this latter concern, and in addition focuses on the desirability of further extending the performance tolerance of integrated head/suspension structures to mechanical variations in the manufacture and assembly of disk drives.
Accordingly, an important object of the present invention is to provide a novel low-mass, gimbaled, micro-head/flexure/conductor assembly which minimizes signal modulation resulting from nonflatness from a disk surface, from accumulated assembly tolerances, from improper alignment of the disk spindle and actuator support bearing, or from other mechanical imperfections which might give rise to unwanted dynamic separation between the transducer and the recording surface of the media.
A correlative object of the invention, in the setting just expressed, is to increase the permissible tolerance on disk run-out, spindle alignment, etc., without impairment of the performance of integrated head/suspension structures.
Another key objective of the invention is to increase permissible dimensional and alignment tolerances in the assembly of integrated head/suspension structures and media in disk drives in order to achieve optimal performance with minimal adjustment and run-in time.
A further object of this invention is to extend the limits on contact pad dimensions without incurring detrimental signal modulation resulting from disk run-out or other mechanical imperfections.
Still another object is to minimize head and media wear by enabling a larger contact pad area and consequently a lower local pressure at the head/media interface.
Still another object of the present invention is to separate the manufacture of head and flexure/conductor structures in order to maximize performance characteristics of each, and to facilitate automated assembly of the one to the other into integrated head/flexure/conductor structures.
An object related to that just stated is to increase the number of heads which may be fabricated by deposition processes on a wafer, thereby correspondingly decreasing manufacturing costs.
Still another object related to the separation of head and flexure/conductor manufacture is to provide a flexure structure formed of various materials, including both deposited ceramic material, and different kinds of otherwise fabricated nonceramic materials selected from the group consisting of a metal, an amorphous glass-like material, a refractory material, a composite material, and combinations thereof. Typical materials within this group include beryllium-copper, phosphor-bronze, diamond-like carbon, and various well-known composites.
Another related object of the invention, suggested above vis-a-vis separating head and flexure manufacture, is to facilitate independent optimization of materials, configurations, and processes in the fabrication of both the heads and the flexure/conductor structures.
A further object of the invention, in a modified form thereof, is to employ selectively applied damping material with respect to a flexure structure, thus to control certain resonance and servo-performance characteristics.
Proposed according to a preferred embodiment of the invention is a micro-head/flexure/conductor assembly, or organization, (for reading and writing information with respect to the recording surface in a rigid magnetic recording medium) which assembly includes a read/write transducer unit, an elongate carrier unit for supporting the transducer unit, and gimbal structure interconnecting and articulating these two units for selected, limited relative movement. Significantly, constituent materials and sizing for these assembly components are chosen in such a manner that the effective mass of the assembly is no greater than about 1.5-milligrams. The definition of "effective mass", as such is employed herein, is found in the text of the '916 patent application referred to hereinabove.
Included in the assembly which has just been outlined is the necessary conductor structure which cooperates with the magnetic components in the transducer unit and which is employed for communicating with the "outside world". Uniquely, a part of this conductor structure in a preferred embodiment, in the form of two laterally spaced conductive ribbons, also forms a portion of the interconnective gimbal structure. In modified forms of the invention, gimbal ribbons formed of dielectric material carry conductive traces. This gimbal structure unites the transducer unit and the carrier unit in a generally parallel planar relationship, and allows limited relative pitch and roll between these two units while at the same time inhibiting relative yaw between the two.
A fulcrum projection formed on a surface in the transducer unit rockingly contacts a surface expanse provided on the carrier unit--these two components cooperating with the conductive ribbons to form the gimbal structure which defines the permitted pitching and rolling that can occur between the two units.
Feet that project from an opposite surface in the transducer unit, preferably formed of a hardened wear-resistant material, are provided for making sliding contact with the recording surface in a disk medium.
These and other important features, objects and advantages which are attained by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawings.